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Despite the huge amount of experimental investigations dedicated to the grafting of organoalkoxysilanes on silica, the characterization of covalent linkages remains a difficult task from a spectroscopic point of view. In most cases, the formation of a covalent link is taken for granted and not discussed. 29Si NMR, IR or UV spectroscopies are commonly used to study the modification of silica surface. Herein we report an unambiguous method to evidence the formation of covalent links. It is based on NMR spectroscopy analysis coupled with a rigorous synthetic grafting protocol.

There is currently a great interest in the preparation of nanostructured magnetic films possessing well-defined structures and controlled properties. Recent progresses in colloidal nanocrystals synthesis and processing have led to new methods for producing films and superstructures made with these materials. Hybrid films have been prepared by organizing functionalized magnetite nanoparticles in large patterns using the Langmuir Blodgett technique. Magnetite nanoparticles with an average particle diameter of 39nm have been prepared and then coated with amphiphilic molecules. The resulting decorated particles, with a hydrophobic outer layer, have proven suitable for being processed by the LB technique. The microstructure and the compacity of the nanoparticle arrays appear to depend on the nature of the organic moiety used to decorate the nanoparticles (carboxylate or phosphonate end-capped stilbene derivatives).

Lysozyme and chitosan were evaluated as cationic polymers for the design of silica-coated alginate capsules. No direct relationship was found between the strength of the bio-organic poly-electrolyte membrane and the stability of capsules after the silica coating, which depends mainly on the nature of poly-cation/silicate interactions.

Functional hybrid coatings have been elaborated from a polymer matrix incorporating iron oxide nanoparticles. Stable aqueous suspensions of goethite (α-FeOOH) nanorods, obtained by controlled precipitation of Fe3+ ions, were introduced in 2-hydroxyethyl methacrylate (HEMA). The films were spin-coated on glass substrates from the solutions prior to a UV light induced free radical polymerization step. Nanoindentation tests were carried out to investigate the mechanical properties of the hybrid coatings. Swelling measurements and Fourier Transformed Infrared Spectroscopy (FTIR) were used to characterize the interface between the iron oxide nanoparticles and the PHEMA matrix. Cross-sectional scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was performed to evaluate the dispersion state of the iron oxide particles through the matrix. From a mechanical point of view, iron oxide nanorods yield to a strong reinforcement effect of PHEMA (increase in modulus and hardness by a factor 2 with 5%vol goethite nanoparticles). Origins of such reinforcement are attributed to the existence of highly favourable interactions at the goethite-PHEMA interface combined with a homogeneous dispersion of the particles. The nature of these interactions and evidences of there influence on the mechanical behaviour of the nanohybrid coatings are reported.

Mesoporous Hybrid Thin Films (MHTF) of a variety of compositions and embedded organic functions are produced by combining sol-gel synthesis, template self-assembly and surface modification. One-pot or post-grafting strategies permit to modify the pore surface behavior. Highly controlled MHTF issued from a reproducible and modular synthesis can be used as building blocks for more complex structures, presenting order at larger scales, and novel properties derived from this multiscale order. Multilayer stacks of MHTF presenting specific and different functions and frameworks located in a well-defined position have been produced by combining sequential film deposition, selective functionalization and dissolution. These systems present new properties such as localized chemistry or modulable photonic crystal behavior.

Ethylene glycol modified precursors, such as tetrakis(2-hydroxyethyl)orthosilicate (EGMS) or bis(2-hydroxyethyl)titanate (EGMT), have distinct advantages in the synthesis of mesoporous materials by sol-gel processing compared to the commercially available tetraalkoxide precursors. The glycols released upon hydrolysis have proven to be compatible with lyotropic surfactant mesophases and in addition, these precursors allow for processing in purely aqueous conditions. Besides the standard characterization of the resulting titania and silica-based materials by XRD, electron microscopy, and nitrogen sorption, the potential of the titania-based materials for catalytic applications was tested using Au/TiO2 catalysts in low temperature CO oxidation reactions.

As part of our ongoing exploration into the field of hybrid organic/inorganic particles as HPLC packing materials, we have recently evaluated the use of porous particles synthesized from the co-condensation of ethylene-bridged alkoxysilanes with tetraethoxysilane [1,2]. By employing 4-100 mol% of hybrid organic/inorganic groups (i.e., O1.5SiCH2CH2SiO1.5) to 96-0 mol% inorganic groups (i.e., SiO2), novel hybrid particles have been prepared and shown to be excellent materials for the preparation of efficient and chemically resilient reversed-phase packing materials.

Mineralized biological concretions have attracted increasing interest because of their outstanding properties. The mineralized concretion of terrestrial isopods is an excellent model for acellular natural composite material. Before the molt terrestrial isopods resorb calcium from the posterior cuticle and store it in concretion within the cranial (head) and caudal (tail) ventral segments. This paper present for the first time an analysis of ultrastructural changes occurring in the caudal ventral segmental (CaVS) concretion of a terrestrial isopod Porcellius chilensis during their formation and degradation. The CaVS concretion of the woodlice Porcellius chilensis was analyzed with respect to their content of inorganic material. It was found that the concretion consists of amorphous calcium carbonate (ACC), and amorphous calcium phosphate (ACP), besides small amounts of water and an organic matrix. The CaVS concretion consists of structurally distinct stratum due to inhomogeneous solubility of ACC within the organic matrix that consists of calcareous knob with reticules elements. The organic matrix plays a role in the structural organization of the concretion and in the stabilization of ACC, which is unstable in vitro. We present an analysis of the distribution of minerals, elements, and organic matrix with in the CaVS concretion by using SEM, XRD, IR and EDS. The decalcification experiments exactly imitated the natural demineralization of the CaVS concretion of the Porcellius chilensis and it is thought that an inhomogeneous solubility of ACC and ACP within the CaVS concretion probably caused by variations in the stabilizing properties of matrix components.

Polystannanes, i.e. organometallic polymers of the chemical formula (SnR2)n, are relatively little explored, although they belong to the rare examples of polymers which are characterized by a backbone of metal atoms which are linked by covalent bonds. We developed a new synthetic route which yields pure linear poly(dibutylstannane) [Sn(Bu)2]n by polymerization of dibutylstannane (dibutyltin dihydride) with the catalyst [RhCl(PPh3)3]. Here, we report that the conversion and the reaction rate of dibutylstannane depends crucially on the temperature and [RhCl(PPh3)3] is also suited for the polymerization of dioctylstannane and didodecylstannane. The polymers thus obtained were characterized by 1H, 13C and 119Sn NMR spectroscopy: Orientation of all polystannanes was achieved by tensile drawing. The orientation was examined by UV-vis spectroscopy with polarized light and X-ray diffraction. Remarkably, the orientation of the backbone depended on the length of the alkyl groups.

A novel chemical route in thin film formation that includes the use of inorganic and organic peroxides and metal organic complexes soluble in supercritical carbon dioxide has been investigated for the deposition of alumina, titania and zirconia thin films at low temperatures (<150°C). The metal organic precursors used include: Al(acac)3, OTi(tmhd)2, and Zr(acac)4. Tert-butyl peroxide, and a 30% aqueous solution of hydrogen peroxide were used as oxidants. Depositions were carried out in a 25 ml hot wall reactor at pressures ranging from 2100 to 3900 psi at 80-140°C. The deposited thin films were investigated by using X-ray photoelectron spectroscopy (XPS) and transmission Fourier transform infrared spectroscopy (FTIR). XPS and FTIR results indicate the formation of metal oxides thin films with some bonded carbon. The deposition temperatures achieved in this process are substantially lower than those used in conventional vacuum deposition techniques making feasible the deposition on temperature sensitive substrates and organic materials required for the development of hybrid organic/inorganic devices. Processing at low temperatures in supercritical carbon dioxide may provide the basis for the development of an alternative, environmentally friendly, thin film deposition technique for the processing of nanostructures.

In this paper, the polymerization kinetics of unsaturated double bonds (C=C) in TiO2- and ZrO2-doped hybrid polymeric thin films during UV irradiation and thermal curing is studied by monitoring the variation of C=C absorption band at 1630 cm-1 using FT-IR spectroscopic technique. Experimental results showed that polymerization of the unsaturated C=C groups in the TiO2- and ZrO2-doped hybrid polymers can be realized by either photo-irradiation or thermal treatment. The UV-induced polymerization process is much faster than thermal curing, but a full conversion of C=C groups into polyacrylate chains cannot be achieved without thermal treatment. The catalytic effect of TiO2 and ZrO2 on promoting the polymerization of C=C groups was observed, and the time of UV exposure and thermal curing for cross-linking C=C bonds was found to decrease with the increase of the concentration of TiO2 and ZrO2. The activation energy of the hybrid material containing varied concentration of TiO2 and ZrO2 was calculated, and the results indicated that TiO2 is more active than ZrO2 in promoting the polymerization of the unsaturated C=C bonds. Finally, the mechanisms for TiO2 and ZrO2 enhancing the material's photosensitivity (i.e. promoting polymerization of C=C bonds) have been proposed and discussed.

A series of structurally-defined laddersiloxanes [1] are presented. Pentacyclic laddersiloxanes were prepared by a stepwise procedure from all-cis-tetraisopropylcyclotetrasiloxanetetraol. All-anti pentacyclic, tetracyclic, tricyclic, and bicyclic laddersiloxanes were obtained by oxidation from respecting all-anti pentacyclic ladder polysilane. Stereocontrolled approach using RS-disiloxanediol as an expanding unit enabled the synthesis of longer laddersiloxanes. Finally, methyl-substituted ladder polysilsesquioxane was obtained by the stepwise transformation from (MePhSiO) 4. The X-ray crystal structures, NMR and IR spectra, and thermal stability of these laddersiloxanes are summarized.

The multifunctionality of hybrid organic-inorganic materials has been clearly demonstrated in recent years. Their application in solar- related devices is a growing research area with important technological implications. Our interest is centered on the interplay between the light-harvesting and hole-conducting properties of conjugated polymers and the wide band gap values observed from different inorganic semiconductor oxides. The materials applied in this work are the combination of semiconductor oxides like TiO2, ZnO, Nb2O5, CeO2 and TiO2-CeO2, and different conjugated polymers like poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) or poly(3,4-ethylenedioxythiophene) (PEDOT). Semiconductor oxides have been applied in different configurations like dense thin films, nanostructured electrodes or as nanoparticles. The conjugated polymers have been chosen depending on their light-harvesting properties (e.g. MEH-PPV) or due to their good electrical conductivity and hole conducting properties (e.g. PEDOT). We have characterized our devices in terms of Voc, Jsc, IV-curves, effect of different atmospheres and device lifetime under simulated sunlight irradiation. Tuning the different device parameters such as type of oxide applied, active layer thickness, starting materials concentration, effect of different atmospheres, effect of UV irradiation, etc., permit the fabrication of devices with well-defined properties. A brief discussion and comparison of hybrid solar cells (HSC) with solid-state Dye Sensitized Solar Cells (ss-DSC) applying nanocomposite materials based on TiO2 and PEDOT, as the electron and hole conducting materials respectively, is also included.

Thermal resistant property of siloxane-modified epoxy compositions designed for long-term and high temperature storage was investigated. In this study, we developed two siloxane-modified epoxy compositions to improve the thermal stability of current epoxy encapsulants. One composition contained silicone epoxy, and the other one was cyclic aliphatic siloxane dianhydride.

We selected triglycidyl ether terminated Phenylmethylsiloxnae-co-dimethylsiloxne (GT-1000), which was compatible with the diglycidyl ether of bisphenol A epoxy (Epon-828), to partial replaced the epoxy resin and was cured by liquid anhydride (MHHPA). In the mean time, we also synthesized 5, 5'-(1, 1, 3, 3-tetramethyl disiloxane-1, 3-dilyl)-bis-norborane-2, 3-dicarboxylic anhydride (A1) as a co-curing agent to cure Epon-828.

The thermal resistance was studied by measuring the increase of yellow index (ΔYI) after thermal treatments. In 110 °C storage experiment for 1000 h, the ΔYI of GT-1000 0.2 equivalent was 1.51, whereas Epon-828/MHHPA (Comp 1) was 6.74. Moreover, The ΔYI of the composition with higher equivalent GT-1000 was only 2.15 after 2000 hours thermal aging. In the cyclic aliphatic siloxane dianhydride co-curing compositions, when A1 was 0.05 and 0.1 equivalent, the ΔYI was 2.28 and 0.72 after 1000 h, respectively. Compared with Comp 1, both GT-1000 and A1 were effective for thermal resistance.

In IR-reflow test, the ΔYI of GT-1000/Epon-828/MHHPA= 0.5/0.5/1 was 0.65 and that of Epon-828/MHHPA was 1.49 after 260 °C for 10 seconds. The results revealed that either the siloxane-modified epoxy or siloxane-modified curing agent had excellent thermal resistant property for high performance LED applications.

The elaboration of organosilica based hybrid monoliths exhibiting a hierarchically structured bimodal porous structure with tunable functionality have been processed via High Internal Polymeric Emulsion (HIPE) process for the first time. Through one pot synthesis, many organic functionalities that can act as network modifiers (Methyl, Dinitrophenylamino, Benzyl, Mercaptopropyl) or co-network formers (Pyrrol) have been anchored to the amorphous silica porous network. The resulting materials have been thoroughly characterized via a large set of techniques SEM, TEM, SAXS, mercury porosimmetry, nitrogen adsorption isotherms, FTIR, 29Si MAS NMR. These sol-gel derived hierarchical open cell functional hybrid monoliths exhibit macroscopic void spaces ranging from 5 up to 30 [.proportional]m and their accessible micro-mesoporosity, reveal hexagonal organisation for the dinitrophenylamino, benzyl, and pyrrol based hybrids. The average condensation degree for these hybrid networks ranges between 86 and 90% yielding shaped monoliths with both good integrity and sufficient mechanical properties to be usable as functional catalytic or chromatographic supports.

High refractive index materials are attractive for many photonic elements. For example, 3D photonic bandgap (PBG) materials have been proposed as the basis of many devices. In order to create complete 3D PBGs, materials enabling high refractive index contrast are needed. We here report on novel high refractive index hybrid polymers. They were synthesized by hydrolysis/polycondensation reactions of organo-alkoxysilanes and Ti alkoxide precursors, resulting in organically modified inorganic-oxidic pre-polymer resins. These can be organically cross-linked by one- or two-photon polymerization (2PP). The latter method enables the writing of arbitrary 3D structures. The introduction of Ti into the inorganic-oxidic network accounts for an increase in the material's refractive index, which could be varied between 1.62 and 1.8. Optical properties such as refractive index and absorption losses were determined on an exemplary material system in the lower refractive index range. The influence of the processing parameters on the degree of organic polymerization, and the refractive index of these novel high index materials was investigated in particular. 3D photonic crystal structures were written for the first time in a high-refractive index hybrid polymer.

A new route to synthesize hybrid silica-based network with bridging organic units via molecular recognition is described. The hydrolysis of two monosilylated complementary base pairs, one bearing an adenine fragment and the other a thymine fragment leads to the formation of a powdered sample that has been characterized by Scanning Electron Microscopy (SEM), Powder X-ray Diffraction (PXRD) FTIR and solid state NMR (1H, 13C and 29Si). This last technique proved to be extremely powerful to directly demonstrate the occurrence of heteroassembly of the nucleobase-based silylated fragments, through the use of two-dimensional 1H double-quanta MAS-NMR that could probe spatial proximities between the thymine NH groups and the adenine NH2 groups.

By inducing phase separation parallel to the sol-gel transition of alkoxy-derived silica systems, gels having both macroporous and mesoporous structures can be obtained. Using poly(acrylamide) (PAAm) as a phase-separation inducer, macro/mesoporous silica gels were synthesized. After solvent exchange by water, the size distribution of mesopores of wet gels was evaluated by thermoporometry using a differential scanning calorimetry (DSC). Alternatively, gels were evaporation-dried after solvent exchange by ethanol or water/ethanol, followed by heat-treatment to completely remove volatile and organic components. Characterization of the dried or heat-treated samples was carried out using a scanning electron microscope (SEM) and by nitrogen adsorption measurements. Experimental results showed that the interaction between PAAm and silica is not so strong as the case of polymers having poly(oxyethylene) chains. The contribution of the secondary phase separation within the crosslinking silica-rich phase was suggested to be responsible for the mesopore formation in the PAAm-silica system.

Aerogels were structurally modified using chemical vapor deposition (CVD) of cyanoacrylate monomers to afford polycyanoacrylate-aerogel nanocomposites. Silica aerogels are low density, high surface area materials whose applications are limited by their fragility. Cyanoacrylate CVD allowed us to deposit a film of organic polymer throughout fragile porous monoliths within hours. Our experiments have shown that polymerization of the cyanoacrylate monomers was initiated by the adsorbed water on the surface of the silica permitting the nanocomposites structures to be formed with little or no sample preparation. We found that the strength of the polycyanoacrylate-aerogel nanocomposites increased thirty two-fold over the untreated aerogels with only a three-fold increase in density and an eight-fold decrease in surface area. Along with the improvement in mechanical properties, the aerogels became less hydrophilic than un-modified aerogels. Polycyanoacrylate-coated aerogels were placed directly into water and did not suffer catastrophic fragmentation as observed with un-modified silica aerogels.